Ischemic heart disease is the leading cause of mortality in the United States and second most common in Israel. Myocardial ischemia prevails when imbalance between oxygen demand and delivery to the myocardium occurs: due to increased oxygen demand beyond what can be delivered by increased coronary flow; due to restriction of blood flow from obstruction or stenosis in the coronary circulation in the face of preserved oxygen demand; or combination of these processes. There are two main causes for restricted blood supply to the myocardium: Epicardial atherosclerotic coronary disease or dysfunctional coronary microcirculation. The two processes are often co-occurring in the same patient given the similarities between the risk factors underlying both. As the blood vessels fail to deliver adequate resting or maximal coronary blood flow, either gradually over many years or abruptly during a course of an acute event, myocardial segmental compromise and thus, global cardiac function deteriorates.